Want to stay on the coast? Homeowners weigh post-Sandy elevation.

Clarke also has strong links to the area where her home flooded. In a brief drive around the neighborhood, she stops to say hello to a distant relative, who is cleaning up after the storm. She remembers her grandmother's home a short distance away in Harbor View – a community also flooded by the storm. And she and her husband often launch kayaks from their backyard and paddle around the harbor.

But for most homeowners, a key factor in determining how to rebuild will be where FEMA decides there might be flooding in the future. The agency is in the process of revamping its flood maps by using technologies such as computer modeling and lasers from space.

"Some of the communities said, we don't believe this new technology, raising the lines to a degree we did not see happen in Katrina," says Mr. Roy, who is also associated with the charity organization International Relief & Development, based in Arlington, Va. "Why build to higher marks?"

A main reason to build to higher flood lines is the loss of financial assistance in case of another flood. FEMA does provide grants to affected households, including some that don't have flood insurance, but to be eligible for future assistance, families then have to purchase flood insurance for a number of years and in many cases abide by state requirements for building codes.

"When faced with the loss of funds, most people take the economically prudent course and incorporate the standards," Roy says. "If you build to the new standards, you get the best insurance rates, and you have the best chance to weather the next storm."

Under federal flood-insurance regulations, if a flooded house is in an area where the waves that inflicted damage were larger than three feet and the home requires more than a 50 percent repair, the homeowner is likely to have to rebuild on a piling foundation and elevate the home in some manner, says Spencer Rogers, a coastal erosion and construction specialist who is involved with North Carolina Sea Grant, which works on coastal issues.

Pilings need to be deeply embedded so that erosion won't weaken them. And the house has to be high enough so a wave won't hit it.

"A very small breaking wave can destroy a building very quickly," Mr. Rogers says. "Added height for the foundation is the only safety factor."

Mr. Pilkey has found in his studies that houses that were built two feet above the 100-year flood level have always survived. "That seems to be the magic number. Everything above that was safe," he says.

In Norwalk where the Clarkes live, officials anticipate that FEMA will require buildings to be elevated about another foot as a result of Sandy.

The Clarkes' house, which is already about seven feet above the mean high tide, may have to be elevated to 14 feet above high water, depending on the FEMA changes, says Joseph Delallo, an official in the building-code enforcement department.

"You are not going to stop the water," Mr. Delallo says. "If you elevate the house, then you don't have to worry about it."

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